Vital signs

The pig’s heart usually started beating again by itself, although some pigs needed a jump-start. There was no effect on physical or cognitive function (Surgery, doi. org/dvhdzs). “After we did those experiments, the definition of ‘dead’ changed,” says Rhee. “Every day at work I declare people dead. They have no signs of life, no heartbeat, no brain activity. I sign a piece of paper knowing in my heart that they are not actually dead. I could, right then and there, suspend them. But I have to put them in a body bag. It’s frustrating to know there’s a solution.” That solution will be put to the test in humans for the first time.  A final meeting this week will ensure that a team of doctors is fully prepared to try it. Then all they have to do is wait for the right patient to arrive. That person will have suffered  a cardiac arrest after a traumatic injury, and will not have responded to attempts to start their heart. When this happens, every member of Tisherman’s team will be paged. “The patient will probably have already lost about 50 per cent of their blood and their chest will be open,” he says. The team sees one of these cases each month. Their chance  of survival is less than 7 per cent. The first step is to flush cold saline through the heart and up  to the brain – the areas most vulnerable to low oxygen. To do this, the lower region of their heart must be clamped and a catheter placed into the aorta – the largest artery in the body – to carry the saline. The clamp is later removed so the saline can be artificially pumped around the whole body. It takes about 15 minutes for the patient’s temperature to drop to 10 °C. At this point they will have no blood in their body, no breathing, and no brain activity. They will be clinically dead In this state, almost no metabolic reactions happen in the body, so cells can survive without oxygen. Instead, they may be producing energy through what’s called anaerobic glycolysis.  At normal body temperatures  this can sustain cells for about  2 minutes. At low temperatures, however, glycolysis rates are so low that cells can survive for hours. The patient will be disconnected from all machinery and taken to an operating room where surgeons have up to 2 hours to fix the injury. The saline is then replaced with blood. If the heart does not restart by itself, as it did in the pig trial, the patient  is resuscitated. The new blood  will heat the body slowly, which should help prevent any reperfusion injuries.  The technique will be tested  on 10 people, and the outcome compared with another 10 who met the criteria but who weren’t treated this way because the team wasn’t on hand. The technique will be refined then tested on another 10, says Tisherman, until there are enough results to analyse. We’ve always assumed that you can’t bring back the dead. But it’s a matter of when you pickle the cells,” says Rhee. Getting this technique into hospitals hasn’t been easy. Because the trial will happen during a medical emergency, neither the patient nor their family can give consent. The trial can only go ahead because the US Food and Drug Administration “ Until now we had always assumed that you can’t bring people back from  the dead” considers it to be exempt from informed consent. That’s because it will involve people whose injuries are likely to be fatal and there is no alternative treatment. The team had to have discussions with groups in the community and place adverts in newspapers describing the trial. People can opt out online. So far, nobody has. Tisherman says he eventually hopes to extend the technique to other conditions. For now, suspended animation is limited to a few hours. But  that’s not to say that more lengthy suspension isn’t possible (see “Will human hibernation ever happen” above?). “We’re trying to save lives,  not pack people off to Mars,” says Tisherman. “Can we go longer than a few hours with no blood flow? I don’t know. Maybe years from now someone will have figured out how to do it, but it will certainly take time.”  ■